CN105165089B

CN105165089B - Method for coordinating uplink resource allocation

Info

Publication number: CN105165089B
Application number: CN201380074880.0A
Authority: CN
Inventors: 周国华; 克里斯特·卡尔福特
Original assignee: Shaoxing Yinchuan Software Development Co ltd
Current assignee: SHAOXING YINCHUAN SOFTWARE DEVELOPMENT Co.,Ltd.
Priority date: 2013-03-20
Filing date: 2013-03-20
Publication date: 2020-07-03
Anticipated expiration: 2033-03-20
Also published as: WO2014146711A1; CN105165089A; EP2944145B1; EP2944145A1

Abstract

The present invention relates to a method of allocating uplink radio resources in a cellular radio communication system, said cellular radio communication system comprising: at least one first cell associated with a first control node and one or more first mobile stations served by the first cell, and at least one second cell associated with a second control node and one or more second mobile stations served by the second cell; and the method comprises the steps of: the first control node grouping the one or more first mobile stations into at least two different groups depending on the interference impact of the first mobile stations on the second cell; the first control node allocating uplink radio resources of the first cell to the one or more first mobile stations based on the packet, thereby obtaining a first radio resource allocation pattern for the one or more first mobile stations; the first control node transmitting a first message comprising the first radio resource allocation pattern; the second control node receiving a first message comprising the first radio resource allocation pattern; and the second control node allocating uplink radio resources of the second cell to one or more second mobile stations based on the first radio resource allocation pattern. Furthermore, the invention also relates to a method in a first control node, a method in a second control node, a first control node device, a second control node device, a computer program, and a computer program product thereof.

Description

Method for coordinating uplink resource allocation

Technical Field

The present invention relates to a method of allocating uplink radio resources in a cellular radio communication system. Furthermore, the invention also relates to a method in a first control node, a method in a second control node, a first control node device, a second control node device, a computer program, and a computer program product thereof.

Background

In a Heterogeneous Network (HetNet) environment, interference scenarios in the Network become more and more complex as more and more cells and mobile stations, such as User Equipments (UEs), become part of the Network. The interference situation, together with the imbalance of Uplink (UL) and Downlink (DL) interference and the huge uplink interference variation, poses a huge challenge to the network.

In order to better utilize the radio resources of small cells (such as micro cells, pico cells and femto cells), different types of coordination mechanisms have been introduced, such as:

-Inter-Cell interference coordination (ICIC) based on frequency domain coordination, which is beneficial for user equipments at Cell edges;

enhanced icic (eicic) based on time domain coordination, which protects the Physical Downlink Control Channel (PDCCH) of small cells, especially in Cell Range Extension (CRE) scenarios;

inter-layer joint scheduling, such as Coordinated Multi-Point (CoMP);

-ICIC based on Carrier Aggregation (CA).

However, none of these mechanisms seizes the main problem of heterogeneous network uplink interference. In heterogeneous networks, it has been found that in the Physical Uplink Shared Channel (PUSCH), small cell user equipments have almost no Uplink limitation since they have no power limitation; the uplink power control is sufficient to compensate for these interferences. Therefore, there is no need to coordinate the radio resources of the macro cell or CoMP of the macro layer to assist the user equipment at the edge of the small cell.

Improving the performance of low-performance user equipment is one of the main objectives of increasing small cells, and another objective is to expand the capacity. The uplink network capacity is limited by the power limit of the user equipment and the link efficiency of the individual links. In the uplink of heterogeneous networks, interference variation is a major problem limiting the efficiency of link adaptation and cannot be solved by the methods listed above.

Compared with a homogeneous macro network, the interference situation in the heterogeneous network mainly differs from that in the homogeneous macro network:

-total uplink interference (IoT) higher than thermal noise;

-the downlink interference from each user equipment is higher;

in CRE case, the user equipments of the small cell have higher unbalanced interference in the downlink, the performance of the control channel is problematic;

in the CRE case, the interference of the macro cell increases with CRE bias as small cell user equipments are farther and use higher power;

in non-CRE case, small cell has higher unbalanced interference in uplink;

the IoT of the small cell varies greatly depending on the scheduling in the macro cell, the variation being the Transmission Time Interval (TTI) level.

Since the cell connection of the user equipment is based on downlink signal strength, such as Reference Signal Received Power (RSRP); for small cell user equipment at the edge of the small cell, the downlink RSRP in the small cell is stronger than the RSRP in the neighboring macro cell, so the interference situation is similar to the user equipment downlink in a homogeneous macro network.

However, in the uplink, since a Macro cell user equipment may be in close proximity to a small cell due to a downlink transmission power difference between the Macro cell (Macro) and the small cell, the uplink transmission power of the Macro cell user equipment is much larger than that of the small cell user equipment. Therefore, the uplink interference in the small cell may be much higher than the uplink signal. This situation is illustrated in fig. 1, where MUEs represent macrocell user equipment, i.e., user equipment served by or connected to a macrocell, and PUEs represent picocell (Pico cell) user equipment, i.e., small cell user equipment.

As illustrated in figure 2, when scheduling a distant macro cell user equipment (MUE2), even if it also has high power, the large path loss of the interfering link may shield the small cell from strong interference, as compared to the high interference case when scheduling the interfering equipment MUE1 near the cell edge.

In the present invention, mobile users near the "victim" small cell are referred to as interfering root users (ICUs). However, the challenge of the uplink in small cells is not the high interference when scheduling these ICUs, but the alternating scheduling of ICUs and non-ICUs (MUE 1 and MUE2 in fig. 2). Large variations in interference levels in small cells can cause IoT variations in small cells within a TTI class.

The fast change of IoT in a small cell can cause uplink scheduling problems. For example, TTI6 in fig. 3, when the small cell is to select a Modulation and Coding Scheme (MCS) for this TTI scheduling, which channel should be referred to by the small cell for signal to interference plus noise ratio (SINR)? In this case there are three options:

1. SINR for a high interference TTI is used, such as TTI5 in FIG. 3. The disadvantages of this option are: since the small cell cannot predict the interference level of TTI6, if the next TTI is low interference, the selected MCS is too conservative and may reduce spectral efficiency.

2. The SINR of a low interference TTI is used, as in TTI4 in fig. 3.

When the small cell selects the SINR for a TTI that experiences low interference, and unfortunately the next TTI is faced with high interference, then this transmission is too aggressive and likely to fail. Even after 8 TTIs, retransmissions may face high interference and the gain of the retransmission cannot overcome the mis-aligned estimation of the radio channel.

3. The average or filtered SINR over a certain number of previous TTIs is used. If the small cell uses the averaged or filtered SINR for the next scheduling, the efficiency will decrease in both interference levels. Too aggressive in high interference TTIs and too conservative in low interference TTIs.

A first solution in the prior art according to the third generation partnership project (3GPP) release 8 ICIC study has been proposed. In the LOAD INFORMATION (LOAD INFORMATION) message for the intra-frequency scenario, a UL Interference Overload Indication (UL Interference Overload Indication) IE and a UL high Interference Indication (UL high Interference Indication) IE are specified for coordinating point-to-point uplink Interference, as illustrated in fig. 4. In the UL high interference indication IE, the first base station (eNB1) indicates which parts of Physical Resource Blocks (PRBs) may cause high interference to the second base station (eNB2), and then the eNB2 may intentionally avoid allocating these PRBs to interference sensitive users.

ICIC is a way of interference coordination in the frequency domain, and the main purpose of the method is to enhance the performance of low-performance user equipment (users at the cell edge). The information of the interaction is also used for interference patterns in the frequency domain. The victim cell may avoid using resources with high interference probability for its interference sensitive users. An example of interference patterns in ICIC is shown in fig. 5, where a base station represented by Macro1 sends messages about frequencies to a base station represented by Macro2, which Macro1 would use to schedule mobile stations that may cause high interference, such as MUEs 1, on the cell border between two cells.

However, the ICIC approach is not very useful for heterogeneous network scenarios because:

no low performance user equipments due to interference in small cells, so there is no need to group small cell user equipments as "cell center" and "cell edge", and small cell "cell edge" users are avoided to use PRBs with high interference probability indicated in High Interference Indication (HII) messages; and

typically the number of user equipments in a small cell is very limited, especially a home base station (HeNB). In-frequency-domain coordination may limit the amount of resources available in one scheduled TTI.

A second solution in the prior art according to 3GPP release 10 is further proposed. Elcic has been developed for coordinating inter-layer interference between macro and small cells, the initial intention of this approach is to protect downlink common channels as well as control channels in small cells. This approach is typically used in CRE situations, where small cell users are still served by small cells, causing the small cells to use more traffic, although the downlink RSRP of the small cells is much lower than the downlink RSRP of neighboring macro cells. The control channel of the small cell is then too poor for small cell user equipment within range of the CRE to use. By having the macro cell suppress transmissions in part of the subframes within the time domain, some small cell user equipments, especially small cell user equipments within the CRE range, can still utilize the downlink control channel in these subframes. This suppression Information forms an ABS Information (ABS Information) IE, which is also included in the load Information message of the 3 GPP.

A negative effect of the eICIC approach is that uplink interference from macro user equipments to small cells is also suppressed in uplink subframes corresponding to downlink muting subframes (ABS), since no macro user equipments are scheduled in those slots since PDCCH is suppressed. An example of interference patterns in eICIC is shown in figure 6.

However, the elcic approach is not very effective for uplink interference in heterogeneous networks because:

-scheduling macro user equipments in non-ABS subframes. Since different users have different interference to the small cell, there is still a huge interference variation in the small cell.

Some macro cell centric user equipments may be allowed to use ABS subframes with limited low power in some cases. However, if the user equipments are close enough to the small cell, the uplink power of the user equipments may still cause interference to the small cell, and thus there may be a large interference variation even in the ABS subframe.

According to a third solution in the prior art, how to coordinate interference on the CA level is discussed. The method mainly comprises the following steps:

-the macro base station is responsible for detecting uplink interference of the MUEs to the small cell base station. The identification of the interfering MUEs allows for frequency-based processing of the interfering sources. There may be situations where some MUEs cannot detect the small cell but may still cause high uplink interference to the small cell. Some mechanisms for identifying these conditions are: (1) the MUE sends scheduling history Information to the small cell, which analyzes it together with the experienced interference, or the small cell sends Overload Information (OI) Information with the interference situation it experiences to the macro cell, which analyzes it together with the scheduling history; (2) MUEs transmit Sounding Reference Signals (SRS), the macro base station transmits Sounding configurations to the small cell, which means that the small cell can decode the received MUESRS to find which MUEs are nearby and interfering; (3) to assist in identifying which MUEs served by the macro base station interfere with the small base station, the macro base station sends signals to the small base station, and uplink radio resources are allocated to MUEs that may be interfering (based on TTI, allocated PRBs, demodulation reference signal (DMRS) configuration, and other possible parameters including timing advance of MUEs, etc.). Once the small base station detects the MUE uplink signal, the small base station returns relevant information (TTI, allocated PRBs, DMRS configuration and interference level) to the macro base station so that the macro base station can identify the interfering MUEs and take appropriate countermeasures to mitigate the interference.

The solution informs other resources, which may be in the same carrier or in different carriers, of (re) scheduling information of an MUE after identifying the MUE with interference. A typical example may be an example of interference of an MUE to a resource used as a Secondary Cell (SCell). The macro base station may decide to change the SCell carrier or deactivate the SCell for the user equipment. By moving aggressive MUEs to different resources (not shared with or interfering with small cell base stations), it is possible to mitigate interference to small cell base stations.

Small cell base stations may also be responsible for interference management, as they know which small cell user equipment (PUE) is interfered, they may reschedule the PUE and/or directly do appropriate power control on the PUE.

However, in this solution, although the macro base station has detected interfering devices and also limited interference within the frequency (or carrier) domain, the information utilization in the small cell is still not optimistic.

Disclosure of Invention

It is an object of the present invention to provide a solution to reduce or solve the drawbacks and/or problems of the prior art solutions.

Another object is to provide a solution that may improve the uplink performance compared to prior art solutions.

According to a first aspect of the present invention, the above object is achieved by a method of allocating uplink radio resources in a cellular radio communication system comprising:

at least one first cell associated with a first control node and one or more first mobile stations served by the first cell; and

at least one second cell associated with a second control node and one or more second mobile stations served by the second cell; and

the method comprises the following steps:

the first control node grouping the one or more first mobile stations into at least two different groups depending on the interference impact of the first mobile stations on the second cell;

the first control node allocating uplink radio resources of the first cell to the one or more first mobile stations based on the packet, thereby obtaining a first radio resource allocation pattern for the one or more first mobile stations;

the first control node transmitting a first message comprising the first radio resource allocation pattern;

the second control node receiving a first message comprising the first radio resource allocation pattern; and

the second control node allocates uplink radio resources of the second cell to one or more second mobile stations based on the first radio resource allocation pattern.

According to a second aspect of the present invention, the above object is achieved by a method for allocating uplink radio resources in a cellular radio communication system by a first control node, the cellular radio communication system comprising:

at least one first cell associated with the first control node and one or more first mobile stations served by the first cell; and

the method comprises the following steps:

grouping the one or more first mobile stations into at least two different groups depending on the interference impact of the first mobile station on the second cell;

allocating uplink radio resources of the first cell to the one or more first mobile stations based on the packet, thereby obtaining a first radio resource allocation pattern for the one or more first mobile stations; and

transmitting a first message including the first radio resource allocation pattern.

According to a third aspect of the present invention, the above object is achieved by a method for allocating uplink radio resources in a cellular wireless communication system by a second control node, the cellular wireless communication system comprising:

at least one second cell associated with the second control node and one or more second mobile stations served by the second cell; and

the method comprises the following steps:

receiving a message including a first radio resource allocation pattern associated with an uplink radio resource allocation of a first cell; and

allocating uplink radio resources of the second cell to one or more second mobile stations based on the first radio resource allocation pattern.

Different embodiments of the invention are defined in the appended dependent claims. Furthermore, any of the methods according to the present invention may also be comprised in a computer program and/or a computer program product, such that a processing module of a suitable device may perform any of the methods described above.

According to a fourth aspect of the present invention, the above object is achieved by a first controlling node device arranged to allocate uplink radio resources in a cellular wireless communication system comprising:

at least one first cell associated with the first controlling node device and one or more first mobile stations served by the first cell; and

at least one second cell associated with a second controlling node device and one or more second mobile stations served by said second cell; and

the first control node device comprises:

means for grouping the one or more first mobile stations into at least two different groups depending on the interference impact of the first mobile station on the second cell;

an allocation module configured to allocate uplink radio resources of the first cell to the one or more first mobile stations based on the packet, thereby obtaining a first radio resource allocation pattern for the one or more first mobile stations; and

a transmission module that transmits a first message including the first radio resource allocation pattern.

According to a fifth aspect of the present invention, the above object is achieved by a second controlling node device arranged to allocate uplink radio resources in a cellular wireless communication system comprising:

at least one second cell associated with the second control node device and one or more second mobile stations served by the second cell; and

the second control node device comprises:

a receiving module that receives a message including a first radio resource allocation pattern related to uplink radio resource allocation of a first cell;

an allocation module that allocates uplink radio resources of the second cell to one or more second mobile stations based on the first radio resource allocation pattern.

The first control node and the second control node may be modified with appropriate changes according to different embodiments of the method.

The present invention provides a scheme that can enhance the uplink performance of a second cell by reducing the variation in interference from a pair of mobile stations in an interfering first cell. The method can utilize simple threshold value to determine the mobile station causing high interference, along with reasonable increase of complexity, the invention can obviously enlarge the capacity of the second cell, and the method is introduced into the network to enlarge the capacity.

The present invention can be used in conjunction with existing interference coordination techniques such as ICIC, eICIC, and CA-ICIC to independently enhance the above-described prior art uplink performance.

In addition to capacity expansion, the present invention can also be used to reduce the necessary margin for reliable transmission of critical information in the communication link, such as handover signaling, detection reporting, etc., enhancing the network performance as perceived by the operator as well as the end user.

Further applications and advantages of the present invention will be apparent from the detailed description that follows.

Drawings

The accompanying drawings are included to illustrate and explain various embodiments of the present invention, in which:

figure 1 illustrates uplink and downlink interference scenarios;

fig. 2 illustrates an uplink low interference situation;

fig. 3 illustrates IoT allocation for a small cell;

FIG. 4 illustrates a load information message;

fig. 5 illustrates interference patterns in an ICIC method;

FIG. 6 illustrates interference patterns in the eICIC method;

fig. 7 illustrates link adaptation based on interference coordination;

FIG. 8 illustrates baseline processing in a one-to-one case;

fig. 9 illustrates baseline processing in a macro cell;

figure 10 illustrates baseline processing in a small cell;

FIG. 11 illustrates processing in a one-to-many case;

FIG. 12 illustrates processing in a many-to-one case;

figure 13 illustrates IoT allocation for macro eICIC based TTIs in small cells;

fig. 14 illustrates processing in the CA case;

fig. 15 illustrates an alternative in the frequency domain.

Detailed Description

To achieve the above and other objects, the present invention relates to a method of allocating uplink radio resources in a cellular wireless communication system, such as a 3GPP Long Term Evolution (LTE) or LTE-advanced system. The cellular system comprises at least one cell of a first type associated with a first control node and one or more first mobile stations served by the first cell, the system further comprising at least one cell of a second type associated with a second control node and one or more second mobile stations served by the second cell.

A typical control node may be a base station, such as an eNB in an LTE system, or may be another control node with a corresponding function, such as a central control entity, such as a virtual base station pool in a cloud-based radio access Network (C-RAN). In addition, the expression that a mobile station is served by a cell means that the mobile station is connected to the network and is reading a control channel of a specific base station covering a specific cell, meaning that the mobile station transmits and receives its data in the cell.

According to a preferred embodiment of the invention, the uplink radio resources of the cellular radio communication system are all frequency/time radio resources, such as physical resource blocks or resource elements. This further illustrates that the first radio resource allocation pattern is a time/frequency radio resource pattern, examples of which are described below. The method comprises method steps in both the first control node and the second control node as illustrated in fig. 7, where fig. 7 shows the processing in the first node and the second node, respectively, and the transfer of information between said nodes. Further, fig. 8 illustrates a system aspect of the present invention in which a first cell (representing a macro cell) and a second cell (representing a pico cell) are illustrated, as well as three first mobile stations served by the first cell. The simple dashed line illustrates a boundary where the first control node considers that the first mobile station causes high interference in the second cell, the first mobile stations within the boundary being denoted ICUs and the first mobile stations outside the boundary being denoted non-ICUs. The first control node would then allocate two of the seven sub-frames shown for the ICU first mobile station. The arrow between the first control node and the second control node indicates that the first message contains a first radio allocation pattern between the first control node and the second control node.

The steps in the first control node according to the invention are: grouping one or more first mobile stations into at least two different groups depending on the interference impact of the first mobile stations on the second cell; allocating uplink radio resources of a first cell to one or more first mobile stations based on the packet, thereby obtaining a first radio resource allocation pattern for the one or more first mobile stations; a first message is transmitted that includes a first radio resource allocation pattern.

Fig. 9 is a flow chart illustrating an embodiment of a method in a first controlling node, where it is checked at every TTI whether a first radio resource allocation pattern is defined or whether an update timer has timed out. If there is no defined pattern or the update timer has timed out, the first control node will identify the ICU and then estimate the amount of resource demand needed to meet the ICU connection quality. If the already existing first radio resource allocation pattern supports the resource requirement or the update timer has not timed out, the first control node may continue scheduling usage of uplink resources according to the defined pattern if there are uplink resources to be scheduled. On the other hand, if there is a difference between the amount of resources required by the ICU and the existing first radio resource allocation pattern, the first control node updates the first radio resource allocation pattern and informs the updated first radio resource allocation pattern to the small cells, and in case there is an update timer, resets the update timer before scheduling any uplink resources.

In summary, the method in the first control node comprises ICU identification (identifying interfering mobile stations of the first type), uplink resource allocation (i.e. pattern formation), and scheduling restrictions on the first mobile station. The formation of the resource allocation pattern and possible updating may utilize the intermediate semi-static update procedure to reflect the traffic change in the first cell and the mobility of the first mobile station. To form the uplink resource allocation pattern, the first cell should first find the ICU (interfering root user) of the second cell, the purpose of this step being to divide the first mobile stations into two or more groups according to their level of interference to the second cell. The main input for packet processing is therefore the uplink interference of the first mobile station to the second cell.

The method of identifying an ICU may include, but is not limited to, one or more of the following parameters:

the downlink received power from the first cell to the first mobile station may determine the distance of the mobile station to the first cell site and the power level used by the mobile station, the downlink received power from the second cell to the first mobile station may determine the received power level in the opposite direction, or the relation between the downlink received power from the first cell and the downlink received power from the second cell can be used in the identification process;

-uplink received power from the first mobile station measured in the first cell and/or the second cell, wherein signals from the mobile station can be used to determine the level of interference caused by the mobile station to the second cell;

the spatial position of the first mobile station, the actual distance to the second cell site can be determined using a number of different positioning methods, e.g. satellite based methods such as GPS (global positioning system), galileo positioning system and beidou satellite positioning system, or wireless network based methods such as OTDOA (observed time difference of arrival) and cell-ID based methods.

The grouping of the mobile stations may also be performed using at least one threshold such that the first radio resource allocation pattern comprises at least two sets of uplink radio resources. The first set of uplink radio resources comprises first mobile stations having a high interference impact on the uplink of the second cell and the second set comprises first mobile stations having a low interference impact on the uplink of the second cell. A suitable dB threshold may be used to distinguish mobile stations, e.g. with respect to the maximum output transmission power ratio between the first cell and the second cell, some practical examples of grouping procedures are given below:

-with the a3 event in LTE, sending a measurement report from the user equipment is triggered when the RSRP of the non-serving cell plus the bias is stronger than the RSRP of the serving cell, wherein the RSRP of the second cell is biased little from the RSRP of the first cell. Those mobile stations that are close to the second cell border are collected. The setting of the adjacent RSRP bias relates to the relative difference between the output power of the first cell and the output power of the second cell and may vary, as the second cell may have to change the output power depending on the coverage of other second cells.

In addition to the downlink power difference, the ICU can be identified by the output power during transmission, e.g. a mobile station on one side of the second cell (closer to the first cell site) has a lower path loss than a mobile station on the other side (further from the first cell site), and therefore using a lower output power causes more interference to the second cell for the same service;

-when the first cell informs the second cell about the mobile station's scheduling information and the SRS or DMRS configuration, the second cell detects the mobile station's uplink signal to measure the strength of the mobile station to the small cell's SRS or DMRS or the like.

When the ICU is identified, the control node of the first cell should also pre-allocate uplink radio resources for the first mobile station, which may include the following two parts:

-amount of resources: the estimation of the resource consumption required for the ICU may be achieved by using statistics of the traffic experienced in the first cell. The simplest approach is to use statistics of PRB usage for all these ICUs and then allocate a corresponding percentage of the uplink radio resources. For example, in the previous measurement period, if the PRB usage rate of the first ICU mobile station amounts to 25%, the control node may allocate one-fourth of a subframe to the ICU;

-resource location: after the amount of resources is determined, the location where the resources are placed should be determined (many aspects may be considered), such as:

○ coordinating resource allocation for other second cells within the coverage of the first cell;

○ coordinating resource allocation among other first cells;

○ Quality of Service (QoS) requirements for ICU traffic.

When the ICU resource amount and the resource position are both determined, the first wireless resource allocation mode is formed. The first cell should then inform the corresponding second cell about the uplink resource allocation pattern, while the resource allocation in the first cell should remain consistent with this pattern. The basic requirements for scheduling the resources of the first cell may be: ICUs can only be scheduled in high-interference subframes allocated in the pattern signalled to the second cell and non-ICUs can only be scheduled in low-interference subframes in said pattern. This limitation ensures stability of the interference in the corresponding second cell.

The corresponding method steps in the second control node according to the invention comprise: receiving a first message comprising the first radio resource allocation pattern and allocating uplink radio resources of a second cell for one or more second mobile stations based on the first radio resource allocation pattern.

Fig. 10 is a flow chart illustrating an embodiment of a method in a second controlling node, wherein any one of the existing first radio resource allocation patterns stored in the first cell is updated every TTI, if the first radio resource allocation pattern is received by the second controlling node. If a new first radio resource allocation pattern is not received in this TTI but there is a received first radio resource allocation pattern, the last received first radio resource allocation pattern should be used.

According to one embodiment, when the second control node receives the first uplink resource pattern, two sets of SINR information for future scheduling of the second mobile station may be saved. If there are high interference subframes in the pattern, the mobile station's SINR is grouped into a high interference TTI SINR, and vice versa. Then, when scheduling is performed in the second cell for the next TTI, the second cell should know whether high interference is encountered according to the first uplink radio resource allocation pattern. The SINR information used for scheduling may be any of the following:

the instantaneous SINR of the subframe of the corresponding subframe type received last, e.g. the scheduling performed in TTI6 in fig. 3, if TTI6 is a high interference subframe, the algorithm may use the mobile SINR of TTI5 in case TTI5 is the latest TTI. If the TTI is a low interference subframe, the algorithm may use the mobile SINR for TTI4 if TTI4 is the most recent TTI.

Filtered SINR of past intra-type subframes, such as the scheduling performed at TTI6 in fig. 3, if TTI6 is a high interference subframe, the algorithm may use the mobile station SINR after filtering TTI5 and TTI2, provided the algorithm has this value. If the TTI is a low interference subframe, the algorithm may use the mobile SINR after filtering TTI4, TTI3, and TTI 1.

Thus, the predictable interference level in the next TTI is known in the second cell, and the second control node is thus able to estimate the channel quality more accurately. The invention is therefore based on the idea that uplink interference variation characteristics have to be exploited and the small cell uplink capacity further enlarged. The inventors have realized that the problem of interference in the uplink of the second cell is an unpredictable behavior originating from interference from the interfering first cell(s). Since the interference in the second cell is very different over time, the second cell should take advantage of and adapt to this change. According to the present invention, if the control node of the second cell knows the uplink resource allocation in the first cell and adapts its own uplink resource allocation based on the first radio resource allocation pattern, it is possible to achieve exploiting and adapting to this change.

The message containing the first radio resource allocation pattern may be transmitted by means of a suitable communication protocol using a wired or wireless communication medium. Examples of communication media are: copper twisted wire, optical fiber, coaxial cable, or wireless transmission, and examples of the communication protocol are ethernet, ADSL (asymmetric digital subscriber line), E1, T1, X2, or S1.

From the previous description of the heterogeneous network, it is noted that the first cell may be a macro cell, while the second cell may be a small cell, such as a micro cell, pico cell or femto cell, etc. Obviously, according to the present embodiment, the maximum output power of the first cell is significantly different compared to the maximum output power of the small cell. Typically, the maximum output power ratio between the first cell and the second cell is greater than 4dB, preferably greater than 6 dB. For example, the difference in the ratio between the macro cell and the micro cell is 8dB, and the difference in the ratio between the macro cell and the pico cell is 22 dB.

Furthermore, the first control node is also responsible for updating the first uplink resource allocation pattern when the uplink interference situation changes. The updating may be based on traffic changes or user packet statistics in the first cell. Meanwhile, an update timer may be used to trigger an update of the first uplink resource pattern. Thus, according to a further embodiment of the invention, the first radio resource allocation pattern may be updated based on one or more parameters relating to any mobile station in the group, said parameters comprising:

traffic load in the first cell, since the mobile station will be using the air interface without interruption, but there is no continuous need for information, the load will vary over time, and thus the resource requirements of the ICU and non-ICU will also vary;

-mobile station grouping statistics in the first cell, wherein the mobility of the user will change the number of ICUs over time, and thus the resource requirements defined for the ICUs;

-one or more further radio resource allocation patterns associated with the further first cells, wherein adjusting the pattern of the further first cells may have a gain such that interference variations in the second cell are minimized;

-updating the timer for timing updating of the pattern.

In case the first control node determines that the first radio resource allocation pattern has to be changed, e.g. for any of the reasons listed above, the first radio resource allocation pattern may be updated by transmitting a new first radio resource allocation pattern by the first control node to the second control node via a wired or wireless communication channel. The second control node may then receive the new first radio resource allocation pattern and change the radio resource allocation to the second mobile station in accordance with the new updated pattern information.

In the above disclosure, the focus is on the scenario of a one-to-one relationship of one macro cell to one small cell. In the following disclosure, when the first type cell is a large cell and the second type cell is a small cell, exemplary embodiments of one-to-many, many-to-one, or many-to-many scenarios are contemplated.

This situation exists when the cellular radio communication system comprises two or more second cells. In this case, the step of grouping may involve: one or more first mobile stations are grouped for each second cell, the step of allocating involving allocating uplink radio resources of the first cell for each second cell, thereby obtaining a first radio resource allocation pattern for each second cell.

Another embodiment of the above is when the cellular radio communication system also comprises two or more first control nodes (many-to-one or many-to-many). In this case, the method according to an embodiment comprises the step of transmitting a second message comprising the first radio resource allocation pattern from the first control node to the other first control nodes receiving said second message. Finally, the other first control node uses the first radio resource allocation pattern in the second message to adapt the second radio resource allocation pattern to the uplink radio resources of the other first cell.

In most cases, especially in the dense small cell scenario, the coverage area of the small cells is very limited and the number of the small cells is very large. This is a typical one-to-many scenario shown in fig. 11. In this case, the large cell may transmit different uplink allocation patterns to the individual small cells. Some basic principles that limit the mode formation in this case may be:

if the ICU has a common area, for example MUE1 in the figure is the ICU of two small cells. Both modes preferably also have common resources for use by these public ICUs;

if the ICU has no common area, e.g. two small cells at both ends and far away, the resources in both modes preferably remain different. In some cases, small cells may be placed within the coverage of more than one large cell, for example small cells added for coverage as shown in figure 12. In this scenario, there may be a conflict of interest in performance between the large and small cells. Mobile stations of large cells in different cells tend to use different patterns to avoid interference from mobile stations in other large cells to guarantee performance, but small cells prefer that large cells use the same pattern for both large cells to minimize high interference subframes to guarantee performance of small cells. This problem can be solved by improvements that increase the negotiation between large cells, e.g. both large cells use the same pattern for the small cell.

eICIC case

When a large (first) macro cell uses ABS mechanism to protect the control channel of a small cell, there are two cases:

1. case 1: there is no scheduled traffic in the downlink and uplink ABS subframes. The ABS subframes for the small cell are interference free in the macro layer (excluding some CRS and other minor interference in the downlink);

2. case 2: with low power ABS, those users near the central macro cell that can use weak signals on the control channel and data channel will still be scheduled. It is clear that these users have a low path loss.

For case 1 above, only small cells close to the macro cell will be interfered by large cell users in non-ABS subframes. These small cells should group subframes into high and low interference subframes using a baseline mechanism to coordinate interference.

For small cells on the macro cell edge in case 1 and case 2, the baseline is different in that there is no interference from the macro layer in the ABS subframes. The IoT pattern in the small cell is shown in fig. 13. The allocation pattern includes three types of subframes: non-interfering subframes in macro cell ABS subframes, low-interfering subframes when non-ICUs are scheduled in the macro cell, and high-interfering subframes when ICUs are scheduled in the macro cell.

Of course, when using macro ABS, in most cases, the small cell will use CRE to expand the cell coverage, in which case the interference gap between low and high interference subframes is reduced. However, it is still necessary to coordinate interference from the large cell in non-ABS subframes for the small cell.

Finally, three types of subframes require the following three sets of SINR information to be stored in the small cell:

-channel quality of a size zone ABS subframe;

-channel quality in low interference subframes;

-channel quality in high interference subframes.

In this scenario, when receiving an ABS pattern information (ABS pattern info) IE and an ICU scheduling pattern (ICU schedule pattern) IE in the small cell, the small cell may group small cell users into two groups, that is: cell center users with better control channel quality in all subframes and cell edge users with worse control channel quality in non-ABS subframes.

In the ABS subframe, every user may be scheduled, but the SINR information should select "channel quality in macro cell ABS subframe". In non-ABS subframes, only cell center users can be scheduled, when the next TTI is the high interference TTI indicated by the ICU scheduling pattern IE, the small cell should select "channel quality in high interference subframe", and if the next TTI is the low interference subframe, should select "channel quality in low interference subframe".

CA situation

To avoid high interference of large (macro) cells on the control channel to small cells, CA techniques provide more flexibility in resource allocation for control and data channels. With more information on the control channel and data channel in multiple carriers and other enablers of the cross-carrier scheduler, the payload information message is sent over the X2 interface, which may allow the data channel and control channel to be coordinated separately.

When the macro PDCCH and the pico PDCCH are concentrated on different carriers, respectively, small cell users may have a sufficiently good PDCCH quality even in a CRE environment. For CA-based uplink ICIC in heterogeneous networks, the proposed scheme also uses "ICU identification" to find the ICU of the small cell. This scheme is a frequency domain coordination based approach that limits ICU resources on some specific carriers and keeps the large cell to small cell interference stable in the frequency domain. This approach is not yet perfect, since the coordination is done on the carrier level, the aim is still limited to improving the performance of low performance small cell user equipments, which is not a bottleneck for the interference problem (the "small cell capacity enlargement" has not been considered yet); in the future, small cells are smaller and smaller, the number of ICUs in the small cells is limited, and interference to the small cells in the TTI is still greatly changed within the range of ICU carriers (high interference carriers).

Fortunately, the present invention is still useful in this scenario and can further improve CA-ICIC efficiency. When multiple carriers are used, more flexibility can be provided to resource grouping on the macro layer and more interference patterns can be formed, as shown in fig. 14.

The invention is applied to the TDD system

In a TDD system, uplink and downlink resources may be shared. The MUEs may use resources used as small cell downlink resources as large cell uplink resources. MUEs that are at different distances from the small cell may cause different levels of downlink interference to small cell mobiles. In this case, the large cell may still utilize the scheme to limit the MUE scheduling characteristics and form an interference pattern to the small cell.

The method and information interaction on the first macrocell side are the same as the baseline processing procedure. The difference is that the method of small cell with the first allocation pattern is also used for downlink scheduling. In this case, the macro cell and the small cell need to interact uplink and downlink spectrum allocations before the invention is used to coordinate the macro cell and the small cell.

Furthermore, it is understood by a person skilled in the art that any of the methods according to the invention may also be implemented in a computer program with code means, which when run by a processing means causes said processing means to perform the steps of the method. The computer program is embodied in a computer-readable medium of a computer program product. The computer-readable medium may include substantially any memory such as ROM (read only memory), PROM (programmable read only memory), EPROM (erasable programmable read only memory), flash memory, EEPROM (electrically erasable programmable read only memory), and a hard disk drive.

Furthermore, the invention relates to a first control node device and a second control node device, which correspond to respective methods in the first control node and the second control node. Each control device comprises suitable means for controlling one or more cells. For example, the apparatus may include a transmission module, a reception module, a processing module, a connection module, a storage module, an interface module, an input module, an output module, and so on.

The first control node device further comprises: means for grouping one or more first mobile stations into at least two different groups depending on the interference impact of the first mobile stations on the second cell; an allocation module configured to allocate uplink radio resources of a first cell to one or more first mobile stations based on the grouping to obtain a first radio resource allocation pattern for the one or more first mobile stations; a transmission module configured to transmit a first message comprising a first radio resource allocation pattern.

The second control node device further comprises: a receiving module that receives a message including a first radio resource allocation pattern related to uplink radio resource allocation of a first cell; an allocation module that allocates uplink radio resources of the second cell to one or more second mobile stations based on a first radio resource allocation pattern.

Finally, it is to be understood that the invention is not limited to the embodiments described above, but relates to and encompasses all embodiments within the scope of the appended independent claims.

Claims

1. A method of allocating uplink radio resources in a cellular wireless communication system, the cellular wireless communication system comprising:

at least one first cell associated with a first control node and a plurality of first mobile stations served by the first cell; and

at least one second cell associated with a second control node and a plurality of second mobile stations served by the second cell; and

the method comprises the following steps:

the first control node grouping the plurality of first mobile stations into at least two different groups depending on the interference impact of the first mobile stations on the second cell;

the first control node allocating uplink radio resources of the first cell to the plurality of first mobile stations based on the packet, thereby obtaining a first radio resource allocation pattern for the plurality of first mobile stations;

the second control node allocating uplink radio resources of the second cell to a plurality of second mobile stations based on the first radio resource allocation pattern;

wherein the first radio resource allocation pattern is a time/frequency radio resource pattern;

wherein the uplink radio resources of the first cell are allocated with at least one threshold value such that the first radio resource allocation pattern comprises at least two sets of uplink radio resources, a first set of uplink radio resources being subject to high interference from the plurality of first mobile stations in the second cell for scheduling only high interference mobile stations, a second set of uplink radio resources being subject to low interference from the plurality of first mobile stations in the second cell for scheduling only low interference mobile stations.

2. The method of claim 1, wherein the first cell is a macro cell and the second cell is a small cell, the small cell comprising a micro cell, a pico cell, or a femto cell.

3. The method of claim 2, wherein a maximum output power ratio between the first cell and the second cell is greater than 4 dB.

4. The method of claim 2, wherein a maximum output power ratio between the first cell and the second cell is greater than 6 dB.

5. The method of claim 1, wherein the grouping is based on one or more parameters in the group, the parameters comprising: a downlink reception power from the first cell to a first mobile station, a downlink reception power from the second cell to a first mobile station, or a relationship between the downlink reception power from the first cell and the downlink reception power from the second cell; uplink received power from a first mobile station measured in the first cell and/or the second cell; and the spatial position of the first mobile station.

6. The method according to claim 1, wherein the uplink radio resources of the cellular wireless communication system are frequency/time radio resources, which comprise physical resource blocks or resource elements.

7. The method of claim 1, wherein the first radio resource allocation pattern is updated based on one or more parameters related to any mobile station in the group, the parameters comprising: traffic load in the first cell, mobile station grouping statistics in the first cell, one or more other radio resource allocation patterns associated with other first cells, and updating a timer.

8. The method of claim 7, wherein the first radio resource allocation pattern is updated by the first control node transmitting a new first radio resource allocation pattern.

9. The method of claim 1, wherein the cellular wireless communication system comprises two or more second cells, wherein

The step of grouping involves: grouping the plurality of first mobile stations for each of the second cells; and

said step of allocating by said first control node involves: allocating uplink radio resources of the first cell for each of the second cells, thereby obtaining a first radio resource allocation pattern for each of the second cells.

10. The method according to claim 9, wherein the cellular wireless communication system comprises two or more first control nodes, and the method further comprises the steps of:

the first control node transmitting a second message comprising the first radio resource allocation pattern;

receiving, by other first control nodes associated with other first cells, the second message including the first radio resource allocation pattern; and

the other first control node uses the first radio resource allocation pattern to adapt a second radio resource allocation pattern to the uplink radio resources of the other first cell.

11. The method of claim 1, wherein the step of transmitting involves: the first message is transmitted over a wired or wireless connection.

12. The method of claim 1, wherein the first and second control nodes are both base stations, or other control nodes with corresponding functionality, the base stations comprising enbs.

13. The method of claim 1, wherein the cellular wireless communication system is a 3GPP system, the 3GPP system comprising LTE or LTE-advanced.

14. A method of allocating uplink radio resources in a cellular wireless communication system by a first control node, the cellular wireless communication system comprising:

at least one first cell associated with the first control node and a plurality of first mobile stations served by the first cell; and

the method comprises the following steps:

allocating uplink radio resources of the first cell to the plurality of first mobile stations based on the grouping, thereby obtaining a first radio resource allocation pattern for the plurality of first mobile stations; and

transmitting a first message including the first radio resource allocation pattern;

15. The method of claim 14, further comprising the steps of:

receiving other messages containing other radio resource allocation patterns of other first cells;

using the other radio resource allocation pattern such that the first radio resource allocation pattern is applicable to uplink radio resources of the first cell; and

transmitting the first radio resource allocation pattern applicable.

16. A method of allocating uplink radio resources in a cellular wireless communication system by a second control node, the cellular wireless communication system comprising:

at least one second cell associated with the second control node and a plurality of second mobile stations served by the second cell; and

the method comprises the following steps:

allocating uplink radio resources of the second cell to a plurality of second mobile stations based on the first radio resource allocation pattern;

17. A first controlling node device arranged to allocate uplink radio resources in a cellular wireless communication system, the cellular wireless communication system comprising:

at least one first cell associated with said first controlling node device and a plurality of first mobile stations served by said first cell; and

at least one second cell associated with a second controlling node device and a plurality of second mobile stations served by said second cell; and

the first control node device comprises:

means for grouping the plurality of first mobile stations into at least two different groups depending on the interference impact of the first mobile station on the second cell;

an allocation module configured to allocate uplink radio resources of the first cell to the plurality of first mobile stations based on the packet to obtain a first radio resource allocation pattern for the plurality of first mobile stations; and

a transmission module configured to transmit a first message comprising the first radio resource allocation pattern;

18. A second controlling node device arranged to allocate uplink radio resources in a cellular wireless communication system, the cellular wireless communication system comprising:

at least one second cell associated with said second control node device and a plurality of second mobile stations served by said second cell; and

the second control node device comprises:

a receiving module configured to receive a message comprising a first radio resource allocation pattern related to an uplink radio resource allocation of a first cell; and

an allocation module configured to allocate uplink radio resources of the second cell to a plurality of second mobile stations based on the first radio resource allocation pattern;